1. Field of the Invention
The present invention relates to optical beam splitters as devices for splitting up an incident optical beam into a plurality of sub-beams.
2. Discussion of the Background Art
Beam splitters are well known in the art and frequently applied in various different optical applications. A typical beam splitter comprises e.g. an etalon tilted 45° with respect to the incident beam. One portion of the incident beam will be reflected and another portion transmits through the beam splitter. The coupling ratio depends on the reflection/transmission properties of the etalon.
Different types of beam splitters can be applied for fiber optic applications. Such fiber optic beam splitters, also called couplers, are generally made up of fused fibers where two or more fibers with at least partially removed claddings are melt together.
U.S. Pat. No. 4,492,439 discloses a polarization independent beam splitter provided by a thin plate of birefringent material having a thickness chosen to interchange the characteristic polarization of the beam between the faces of the plate. The reflection/refraction ratio at the two boundaries are then complementary and the combined effect is insensitive to the polarization of the incident beam in the Brewster angle.